Computers, including personal computers, have a wide application of uses and are increasingly in demand. Most of these computers have associated with them a display device and a keyboard input device. Further, pointing devices may be used with these computers. Such conventional pointing devices include devices known as a mouse, a track ball, a digitizing tablet, a light pen, a touch screen and the like. These pointing devices require the use of either a printed circuit board (hardware) that plugs into the internal bus of the computer (bus mouse) or the use of a serial, RS-232, port of the computer (serial mouse) making the serial port unavailable for other uses such as modems and the like. In other cases, the pointing devices require a software driver, always resident in the computer, to bridge the output from the bus electronics, in the case of a bus mouse, or from the serial port, in case of the serial mouse, to the application software. Special arrangements must be made in the application software to accept inputs from pointing devices. For this reason, not all application software allows the use of a pointing device.
The present invention overcomes the disadvantages of the prior art by providing adapter electronics coupled between the computer and the pointing device and the keyboard. While the invention can be applied to any computer system that has a display and keyboard input device with cursor keys (such as video terminals attached to mini and main frame computers), it will be discussed herein in relation to personal computers. The pointing device and the keyboard plug into the adapter electronics which, in turn, plugs into the personal computer through the normal keyboard port. Thus, no internal electronics is required, as is the case with a bus mouse, and the serial port is not used, as in the case with a serial mouse. No software driver is required, thereby avoiding the conflicts that sometime arise when additional resident software functions are loaded into the personal computer. Further, no special arrangements are necessary in the application software. If the application software accepts or reacts to cursor keys, as most commercially available software does, it can also use pointing devices with the present invention. No external power supply is required since the power is supplied by the personal computer.
The adapter electronics converts signals from the pointing device into codes corresponding to keyboard key actuations. In this manner, the user may perform all functions of the application software that can be done with keyboard cursor keys except with much greater convenience and speed. In addition to signals from the pointing device, the adapter electronics accepts key codes generated by the keyboard and passes them on unmodified to the personal computer. In this manner, all normal keyboard functions are available to the user. Most commercially available application software accepts cursor key codes generated by the keyboard.
There are two major types of pointing devices commercially available. The first type generates two pulse trains for each vertical and each horizontal motion. In accordance with standard practice, the phasing of the two pulse trains indicates direction of motion. These pulse trains are generated in response to motion of the pointing device. This type of pointing device is conventionally called a "bus mouse" since an electronics card, plugged into the bus of the personal computer, is necessary to accept the pointing device signals.
The second type of pointing device generates ASCII codes in serial, ASCII coded format using the RS-232 protocol. These codes are transmitted by the pointing device and indicate the distance moved in vertical and horizontal directions. The present invention is not dependent on the type of signals generated by the pointing device. Any type of signal generated by a pointing device can be converted into cursor key codes. The present invention converts the pointing device signals into cursor key codes corresponding to those generated by the keyboard.
Many conventional pointing devices have one or more switches which the user can activate to cause reactions in the software. The present invention can accept any number of switch closures, in addition to the pointing device signals, and generate codes to the personal computer as if certain keys or key combinations were pressed on the main keyboard itself. The same circuit that merges the key codes generated from the pointing device signals into the personal computer's keyboard input terminal is used to merge the key codes generated from switch closures on the pointing device.
Thus, the present invention relates to adapter electronics that converts pointing device signals into cursor key code signals corresponding to cursor key code signals generated by keyboard cursor key actuations and couples them selectively to a common terminal in the personal computer. It is, therefore, a major object of the present invention to provide adapter electronics for a personal computer system which allows a pointing device and a keyboard to be coupled to the personal computer through a common port.